Capsules for containing beverage ingredients are well known. One type of known capsule is described in U.S. Pat. No. 5,840,189 and comprises a cup-shaped capsule body having a base, a truncated conical side wall and an open mouth. The open upper mouth is hermetically sealed by a lid. The cup-shaped capsule body and lid define a capsule volume in which is located a filter element and a portion of beverage ingredients. In use, the lid and base are both pierced to allow for the injection of hot water into the capsule volume, and the delivery of an extracted beverage out of the capsule volume. The filter element serves to allow the extracted beverage to pass there through while retaining the solid residue of the beverage ingredients. In U.S. Pat. No. 5,840,189 the filter element is permanently joined to an interior surface of the conical side wall at a location adjacent to the open mouth.
U.S. Pat. No. 6,440,256 describes a method of forming and inserting a filter element into a cup-shaped capsule body of the type described in U.S. Pat. No. 5,840,189. In particular, the method first requires the folding and sealing of a filter material to form a filter element. The filter element is then transferred to the location of a cup-shaped capsule body by a first mandrel. A probe is then lowered relative to the first mandrel to strip the filter element off the first mandrel with a heated tip of the probe being used to tack weld a bottom of the filter element to the base of the cup-shaped capsule body. Next, the probe is withdrawn and a shaping mandrel is inserted to radially expand the filter element against the interior side wall of the cup-shaped capsule body. The shaping mandrel is then withdrawn and a welding mandrel is inserted to effect a peripheral weld between the filter element and the side wall.
This prior art method involves a number of individual stages and require three separate mandrels. It is also unsuitable for assembling a filter element in a capsule where the filter element does not extend to the base of the cup-shaped capsule body.